ZAP‐70 Genotype Disrupts the Relationship Between Microbiota and Host, Leading to Spondyloarthritis and Ileitis in SKG Mice

Abstract

Objective. The spondyloarthritides share genetic susceptibility, interleukin-23 (IL-23) dependence, and the involvement of microbiota. The aim of the current study was to elucidate how host genetics influence gut microbiota and the relationship between microbiota and organ inflammation in spondyloarthritides.Methods. BALB/c ZAP-70 W163C -mutant (SKG) mice, Toll-like receptor 4 (TLR-4)-deficient SKG mice, and wild-type BALB/c mice were housed under specific pathogen-free conditions. SKG and wild-type BALB/c mice were maintained under germ-free conditions, and some of these mice were recolonized with altered Schaedler flora. All of the mice were injected intraperitoneally with microbial ␤-1,3-glucan (curdlan). Arthritis, spondylitis, and ileitis were assessed histologically. Microbiome composition was analyzed in serial fecal samples obtained from mice that were co-housed beginning at the time of weaning, using 454 pyrosequencing. Infiltrating cells and cytokines in the peritoneal cavity were measured by flow cytometry and enzyme-linked immunosorbent assay. Cytokine, endoplasmic reticulum (ER) stress marker, and tight junction protein transcription was measured by quantitative real-time polymerase chain reaction.Results. Microbiota content and response to curdlan varied according to whether T cell receptor signal strength was normal or was impaired due to the ZAP-70 W163C mutation. Curdlan triggered acute inflammation regardless of the presence of the SKG allele or microbiota. However, no or limited microbiota content attenuated the severity of arthritis. In contrast, ileal IL-23 expression, ER stress, lymph node IL-17A production, goblet cell loss, and ileitis development were microbiotadependent. Ileitis but not arthritis was suppressed by microbiota transfer upon co-housing SKG mice with wild-type BALB/c mice, as well as by TLR-4 deficiency.Conclusion. The interaction between immunogenetic background and host microbiota leads to an IL-23-dependent loss of mucosal function, triggering ileitis in response to curdlan.The human genome has been shaped by interaction with commensal and pathogenic microorganisms. Spondyloarthritides (SpA) are strongly heritable conditions affecting 2% of the population and include ankylosing spondylitis (AS), psoriatic arthritis, reactive arthritis, uveitis, and arthritis associated with inflammatory bowel disease (IBD) (1). The genetic associations of these diseases overlap and identify genes essential for host microbial defense, including class I major histocompatibility complex, antigen processing, T cell signaling, interleukin-23 receptor (IL-23R), caspase recruitment domain 9, and NF-B (2). Although clinical

Proinflammatory CX3CR1+CD59+Tumor Necrosis Factor–Like Molecule 1A+Interleukin‐23+ Monocytes Are Expanded in Patients With Ankylosing Spondylitis and Modulate Innate Lymphoid Cell 3 Immune Functions

“…naïve SKG mice are healthy, they have fecal microbial dysbiosis relative to control BALB/c mice, and IL-23 is constitutively expressed in the ileum [13]. In naïve SKG mice, …”

“…Accordingly to our previous demonstration, [11] in the inflamed ileum of AS patients, despite a global expansion of MNP ( figure 1A-B), we observed a significant down-regulation of CD14 expression ( Figure 1A-B) compared to healthy controls (supplemental Figure 1A). Due to the low levels of CD14 monocyte expression in AS gut, we enthesitis, psoriasiform inflammation of the skin and Crohn's-like ileitis [13][14]. Although…”

Genetics of ankylosing spondylitis—insights into pathogenesis

“…62 Similarly, in the SKG mouse model of spondyloarthritis, germfree conditions dampen disease considerably and reduce ileal IL23 expression. 63 It remains a possibility that the altered microbiome is the result of the disease process itself and is independent of genetic imprinting. Nevertheless, understanding what shapes the microbial composition of the gut in patients with AS is a prerequisite to any potential therapeutic manipulation of the gut microbiome.…”

Inflammation-driven bone formation in ankylosing spondylitis: characterisation of the proteoglycan-induced spondylitis mouse model

“…Germ-free environment has been shown to prevent ileitis and significantly reduce the severity of curdlan-induced spondylitis and arthritis [63]. Increase in highly self-reactive CD4+ T cells induced by the ZAP-70 mutation alone is not sufficient for full disease development and incidence in this model as neutrophils, macrophages, IL-1, IL-6, IL-17…”

“…[61]. HLA-B27/h2m transgenic rats [62] and SKG mice [63], two SpA animal models, have reduced intestinal inflammation as well as arthritis when raised in a germ-free environment suggesting the gut microbiome play important roles in disease development. Moreover, the very distinct gut microbiome populations in both models prior to disease onset support that microbial signature was altered by genetic background [63,64].…”